Research On Voltage Optimization Strategy Of Distributed Photovoltaic Distribution Network

Energy is the basis of industrial production and modern society development and operation,but the large-scale exploitation and utilization of traditional fossil fuels make the society face increasingly serious energy crisis and environmental problems.It is urgent to develop the distributed photovoltaic grid-connection technology,but the distributed photovoltaic grid-connection brings opportunities to the distribution network,but also brings great challenges to the stable and safe operation of the distribution network.The traditional voltage regulation mode of the distribution network is difficult to meet the requirements of the distribution network with high permeability distributed photovoltaic for rapid and flexible voltage regulation.In order to control the voltage more efficiently,this thesis aims at a series of problems existing in grid-connected distributed photovoltaic,and has completed the following research work:Firstly,the influence of distributed photovoltaic grid-connection on the distribution network is studied.The influence of photovoltaic grid-connection on the operation characteristics of distribution network is analyzed.The voltage distribution law of each node of the distribution network after single or multiple distributed PV gridconnected is obtained.Four possible voltage distributions on distribution network lines can be obtained by comparing distributed PV active power output with the sum of afterload active power of access points.The formula for calculating the loss of single and multiple distributed photovoltaic networks after grid-connection is derived.It is pointed out that the optimal access point is actually close to the head end of the line with the increase of photovoltaic active power output.Then,three kinds of simulation schemes are analyzed to verify the influence law of photovoltaic grid-connection on the voltage distribution and network loss of the distribution network under different permeability and grid-connection position,and analyze the influence of distributed photovoltaic on the voltage distribution of the distribution network when it is connected through a series of special nodes.Secondly,a distributed photovoltaic optimal allocation method based on improved Grey Wolf algorithm(LIGWO)is proposed.Firstly,the optimal configuration was modeled,and the minimum voltage deviation and minimum network loss were taken as objective functions.The weight analysis method was used to carry out multiobjective normalization processing,and a series of constraints including power flow constraints,safety constraints and capacity constraints were considered.Then,the process and problems of traditional GWO algorithm are described.Tent chaotic mapping,nonlinear control parameter strategy and Levy flight are introduced to improve the algorithm,and the optimization ability of the algorithm is verified by simulation.Finally,the example model and parameter Settings and the process of the improved Gray Wolf algorithm(LIGWO)in distributed photovoltaic optimal configuration are given.Three sets of simulation are carried out to verify the effectiveness of the improved gray Wolf optimization algorithm,multi-objective function processing method and comprehensive optimal configuration method proposed in this thesis.Finally,a two-stage reactive voltage optimization strategy considering the residual capacity of photovoltaic grid-connected systems is proposed.In order to solve the difficulty of voltage regulation of traditional voltage regulating equipment in photovoltaic distribution network with high permeability,the reactive power and active power regulation ability of photovoltaic grid-connected system under three states is studied,and a three-state cooperative operation model of photovoltaic grid-connected system is proposed.Considering the operation characteristics of traditional voltage regulating equipment,the model was built,the minimum voltage deviation and fluctuation was taken as the target and the multi-objective normalization was carried out by the judgment matrix method.The action plan of discrete equipment such as capacitors and reactors was made in the next 24 hours before the day,the real-time short-term scheduling was completed within the day,and the output of photovoltaic grid-connected system was adjusted to further adjust the voltage of the distribution network.Through simulation analysis,the optimization strategy proposed in this thesis can achieve the expected effect,which can effectively reduce the voltage deviation and fluctuation of distributed photovoltaic distribution network,and verify the effectiveness and feasibility of multi-state regulation model participating in voltage regulation.